Demon carb CFM question

The difference seems to be in the throttle bores (eg http://www.demoncarbs.com/1904.asp) 1 3/8 vs 1 11/16 but the venturis are not published. Someone knows, but I don't.
In any event, the rating is based on air flow at wide open throttle under a specified pressure difference.

If you plan to be running this engine at high rpm (4500 - 6000) as you might on the drag strip, then the 750 should produce more power. However if the cam and exhaust and gearing are such that peak hp is at 4500 or less, then IMO the 750 will gain you nothing even at the track.

The 625 with a smaller throttle ought to produce a slightly better quality idle and off-idle and get onto the primary system quicker. This should give it an edge in efficiency and throttle response. I would e-mail or call them to see what they say.

Basically, its like a T-quad. Unless you are switching to a squarebore intake, the T-quad should be just as good.